Frequency mixing device

ABSTRACT

Provided is a FET resistive frequency mixing device having improved RF-LO and IF-LO isolations. The frequency mixing device includes: a field effect transistor (FET), a local oscillation matching circuit connected to a gate of the FET to transfer a local oscillation signal to the gate of the FET, a gate biasing circuit connected to the gate of the FET, a radio frequency (RF) matching circuit having a first terminal connected to a drain side of the FET and a second terminal serving as a RF terminal to receive or output a RF signal, an intermediate frequency (IF) matching circuit having a first terminal connected to the drain side of the FET and a second terminal serving as an IF terminal to receive or output an IF signal, and a series resonance circuit providing a path from the drain of the FET to ground for the local oscillation signal.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims a convention priority based on KoreanPatent Application No. 10-2020-0131357 filed on Oct. 12, 2020, with theKorean Intellectual Property Office (KIPO), the entire content of whichis incorporated herein by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a frequency mixing device and, moreparticularly, to an FET resistive frequency mixer.

2. Description of Related Art

A frequency mixer, which is an essential device in a wirelesscommunications system, may convert an intermediate frequency (IF) signalinto a radio frequency (RF) signal or vice versa. Types of conventionalfrequency mixers may include a passive frequency mixer employing adiode, an active frequency mixer employing a field effect transistor(FET), and a FET resistive frequency mixer.

The FET resistive frequency mixer performs a frequency mixing by using alinear transconductance region in an I-V characteristic curve the FET towhich no drain bias is applied, and thus reveals characteristics ofinherently high linearity and low DC power consumption. When a localoscillation (LO) signal is applied to a gate of the FET in the FETresistive frequency mixer to turn on and off the FET, a frequency of anIF signal or RF signal applied to a drain of the FET is mixed with thefrequency of the LO signal due to a time-varying resistance of the FET.A frequency mixer having a high linearity is preferable since such afrequency mixer allows use of an input signal of higher power.

FIG. 1 shows a typical FET resistive frequency mixer. In the FETresistive frequency mixer of FIG. 1 , a local oscillation signal isapplied to a gate of a field effect transistor (FET) 110 through an LOmatching circuit 120. The gate of the FET 110 is biased by a gatebiasing circuit 130. A drain of the FET 110 is not biased and connectedto ground via a radio frequency choke (RFC) so as to maintain anunbiased state. An RF input/output terminal and an IF input/outputterminal are connected to the drain of the FET 110 through a RF matchingcircuit 150 and an IF matching circuit 160, respectively. In case of afrequency upconversion, an IF input signal is applied through the IFmatching circuit 160 and mixed with the LO signal at the drain of theFET 110, and an RF output signal is output through the RF matchingcircuit 150. In case of a frequency downconversion, an RF input signalis applied through the RF matching circuit 150 and mixed with the LOsignal at the drain of the FET 110, and an IF output signal is outputthrough the IF matching circuit 160.

However, in such a FET resistive frequency mixer, an LO signal componentmuch larger than the RF signal may appear at the RF output terminal.Thus, it is necessary to remove the LO signal component by the RFmatching circuit. This figure of merit to cancel the LO signal componentis referred to as a RF-LO isolation. In order to improve the RF-LOisolation by the RF matching circuit, a larger and more complex RFmatching circuit may be required. For this reason, it is difficult toimplement a small and lightweight frequency mixer. In particular, thedifficulty in improving the isolation becomes greater in case of anintegrated circuit (IC) chip type product such as a frequency mixermonolithic microwave integrated circuit (MMIC).

SUMMARY

Provided is a FET resistive frequency mixing device having improvedRF-LO and IF-LO isolations by using a small-sized band-stop filter.

According to an aspect of an exemplary embodiment, a frequency mixingdevice includes: a field effect transistor (FET) having a gate, a drain,and a source, a local oscillation matching circuit connected to the gateof the FET to transfer a local oscillation signal to the gate of theFET, a gate biasing circuit connected to the gate of the FET to bias thegate of the FET, a radio frequency (RF) matching circuit having a firstterminal connected to a drain side of the FET and a second terminalserving as a RF terminal to receive or output a RF signal, anintermediate frequency (IF) matching circuit having a first terminalconnected to the drain side of the FET and a second terminal serving asan IF terminal to receive or output an IF signal, and a series resonancecircuit providing a path from the drain of the FET to ground for thelocal oscillation signal.

The series resonance circuit may include a capacitor and an inductorconnected in series.

The frequency mixing device may further include a band-stop filterhaving a first terminal connected to the drain of the FET and a secondterminal connected to the RF matching circuit or the IF matching circuitto reduce the local oscillation signal transferred to the secondterminal of the band-stop filter.

The band-stop filter may block or reflect at least some portion of thelocal oscillation signal received by the band-stop filter.

The band-stop filter may be disposed between the drain of the FET andthe first terminal of the RF matching circuit or between the drain ofthe FET and the first terminal of the IF matching circuit.

The band-stop filter may be formed in a spiral shape using a spurline.

The RF matching circuit may include a high-pass filter or a band-passfilter configured to deliver a RF output signal having a frequency inwhich a frequency of the IF signal and a frequency of the localoscillation signal are mixed.

The IF matching circuit may include a low-pass filter or a band-passfilter configured to deliver an IF output signal having a frequency inwhich a frequency of the RF signal and a frequency of the localoscillation signal are mixed.

The frequency mixing device may further include a drain groundingcircuit connected to the second terminal of the band-stop filter toprovide a path from the second terminal of the band-stop filter toground.

The drain grounding circuit may include a radio frequency choke (RFC).

The RF matching circuit or the IF matching circuit may include agrounding path configured to selectively connect the drain side of theFET to ground.

According to an exemplary embodiment of the present disclosure, theRF-LO isolation and the IF-LO isolation of the FET resistive frequencymixing device may be improved by using a small-sized band-stop filter.In particular, it is possible to enhance the RF-LO isolation and theIF-LO isolation without using any complex circuit disposed internally orexternally. The FET resistive frequency mixing device employing thesmall-sized band-stop filter according to an exemplary embodiment of thepresent disclosure may be applicable to a hybrid microwave integratedcircuit (HMIC) device as well as a monolithic microwave integratedcircuit (MMIC) device.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a circuit diagram of a typical FET resistive frequency mixer;

FIG. 2 is a circuit diagram of a FET resistive frequency mixer accordingto an exemplary embodiment of the present disclosure;

FIG. 3 illustrates a layout of a semiconductor microwave monolithicintegrated circuit (MMIC) band-stop filter according to an exemplaryembodiment of the present disclosure;

FIG. 4 is a graph illustrating an insertion loss simulation result of aband-stop filter shown in FIG. 2 ;

FIG. 5 is an exemplary layout of a semiconductor monolithic microwaveintegrated circuit (MMIC) for implementing the FET resistive frequencymixer according to an exemplary embodiment of the present disclosure;

FIG. 6 is a graph showing a simulation result for an isolationperformance of the FET resistive frequency mixer including a seriesresonance circuit but not including a band-stop filter; and

FIG. 7 is a graph showing a simulation result for the isolationperformance of the FET resistive frequency mixer including both theseries resonance circuit and the band-stop filter.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

For a more clear understanding of the features and advantages of thepresent disclosure, exemplary embodiments of the present disclosure willbe described in detail with reference to the accompanied drawings.However, it should be understood that the present disclosure is notlimited to particular embodiments disclosed herein but includes allmodifications, equivalents, and alternatives falling within the spiritand scope of the present disclosure. In the drawings, similar orcorresponding components may be designated by the same or similarreference numerals.

The terminologies including ordinals such as “first” and “second”designated for explaining various components in this specification areused to discriminate a component from the other ones but are notintended to be limiting to a specific component. For example, a secondcomponent may be referred to as a first component and, similarly, afirst component may also be referred to as a second component withoutdeparting from the scope of the present disclosure. As used herein, theterm “and/or” may include a presence of one or more of the associatedlisted items and any and all combinations of the listed items.

When a component is referred to as being “connected” or “coupled” toanother component, the component may be directly connected or coupledlogically or physically to the other component or indirectly through anobject therebetween. Contrarily, when a component is referred to asbeing “directly connected” or “directly coupled” to another component,it is to be understood that there is no intervening object between thecomponents. Other words used to describe the relationship betweenelements should be interpreted in a similar fashion.

The terminologies are used herein for the purpose of describingparticular exemplary embodiments only and are not intended to limit thepresent disclosure. The singular forms include plural referents as wellunless the context clearly dictates otherwise. Also, the expressions“comprises,” “includes,” “constructed,” “configured” are used to refer apresence of a combination of stated features, numbers, processing steps,operations, elements, or components, but are not intended to preclude apresence or addition of another feature, number, processing step,operation, element, or component.

Unless defined otherwise, all terms used herein, including technical orscientific terms, have the same meaning as commonly understood by thoseof ordinary skill in the art to which the present disclosure pertains.Terms such as those defined in a commonly used dictionary should beinterpreted as having meanings consistent with their meanings in thecontext of related literatures and will not be interpreted as havingideal or excessively formal meanings unless explicitly defined in thepresent application.

Exemplary embodiments of the present disclosure will now be described indetail with reference to the accompanying drawings.

FIG. 2 is a circuit diagram of a FET resistive frequency mixer accordingto an exemplary embodiment of the present disclosure. The FET resistivefrequency mixer according to an embodiment of the present disclosure mayinclude a field effect transistor 210 having a source (S), a gate (G),and a drain (D), an local oscillation (LO) matching circuit 220, a gatebiasing circuit 230, a series resonance circuit 240, and a band-stopfilter (BSF) 250, a drain grounding circuit 260, a radio frequency (RF)matching circuit 270, and an intermediate frequency (IF) matchingcircuit 280.

The LO matching circuit 220 may be connected to the gate of the FET 210and transfer a local oscillation signal to the gate of the FET 210. Thegate bias circuit 230 may be connected to the gate of the FET 210 tobias the gate of the FET 210.

The gate of the FET 210 is connected to LO matching circuit 220 toreceive the local oscillation signal. The drain of the FET 210 may beconnected to an RF terminal through the RF matching circuit 270 and theband-stop filter 250. In addition, the drain of the FET 210 may beconnected to an IF terminal through the IF matching circuit 280 and theband-stop filter 250. In the case of a frequency upconversion, the FET210 may mix the local oscillation signal to an IF input signal receivedthrough the IF terminal and the IF matching circuit 280 to output an RFoutput signal resulting from a frequency mixing through the RF matchingcircuit 270 and the RF terminal. In the case of a frequencydownconversion, the FET 210 may mix the local oscillation signal to anRF input signal received through the RF terminal and the RF matchingcircuit 280 to output an IF output signal resulting from the frequencymixing through the IF matching circuit 280 and the IF terminal.

The series resonance circuit 240, which includes a capacitor and aninductor connected in series, may be connected to the drain of the FET210. The series resonance circuit 240 resonates at a local oscillationfrequency and provides a grounding path for the local oscillationsignal. Thus, the series resonance circuit 240 allows a portion of thelocal oscillation signal passed from the gate of the FET 210 through agate-drain capacitance of the FET 210 to flow to the ground. Theband-stop filter 250, which has a first terminal connected to the drainof the FET 210, may block the local oscillation signal having passed theseries resonance circuit 240 to enhance a RF-LO isolation and an IF-LOisolation.

The drain grounding circuit 260, which may include a radio frequencychoke (RFC), may be connected to a second terminal of the band-stopfilter 250 and provide a path from the second terminal of the band-stopfilter 250 to ground so that the drain of the FET 210 remains unbiased.The drain grounding circuit 260 may be omitted in case that the RFmatching circuit 270 or the IF matching circuit 280 has a grounding pathsimilar to the drain grounding circuit 260.

The RF matching circuit 270 has a first terminal connected to the secondterminal of the band-stop filter 250 and a second terminal for receivingor outputting an RF signal. The second terminal of the RF matchingcircuit 270 may be the RF terminal of the FET resistive frequency mixer.The RF matching circuit 270 may be implemented by a high-pass filter ora band-pass filter. The IF matching circuit 280 has a first terminalconnected to the second terminal of the band-stop filter 250 and asecond terminal for receiving or outputting an IF signal. The secondterminal of the IF matching circuit 270 may be the IF terminal of theFET resistive frequency mixer. The IF matching circuit 280 may beimplemented by a low-pass filter or the band-pass filter (BPF). In thecase of the frequency upconversion, the IF terminal, i.e. the secondterminal of the IF matching circuit 280, receives the IF input signal,and the RF terminal, i.e. the second terminal of the RF matching circuit270 outputs the RF output signal resulting from the frequency mixing. Inthe case of the frequency downconversion, the RF terminal, i.e. thesecond terminal of the RF matching circuit 270, receives the RF inputsignal, and the IF terminal, i.e. the second terminal of the IF matchingcircuit 280 outputs the IF output signal resulting from the frequencymixing.

According to the frequency mixer described above, the series resonancecircuit 240 may improve the LO isolation by removing a portion of thelocal oscillation signal, and the band-stop filter 250 may furtherenhance the RF-LO isolation and the IF-LO isolation by reflecting thelocal oscillation signal.

In an exemplary embodiment, a FET resistive frequency mixer converting a7 GHz IF signal to a 30 GHz RF signal was designed, and varioussimulations were performed on the frequency mixer. The design andsimulation results will now be described with reference to FIGS. 3 to 7.

FIG. 3 shows a layout of a semiconductor microwave monolithic integratedcircuit (MIMIC) band-stop filter according to an exemplary embodiment ofthe present disclosure.

It is desirable that the band-stop filter has a small size to enable toimplement in a single-chip monolithic microwave integrated circuit(MMIC) and blocks 23 GHz local oscillation frequency signal at an outputstage of the frequency mixer. In order to reduce the size, the band-stopfilter 250 was formed in a spiral shape using a spurline having a lengthof λ/4. Here, λ may denote a wavelength corresponding to a centerfrequency of the band-stop filter. In addition, the spurline structureof the band-stop filter 250 was disposed in duplicate, as shown in FIG.3 , to improve the isolation of the local oscillation signal. However,the form of shaping the band-stop filter 250 is not limited thereto.

FIG. 4 is a graph showing an insertion loss simulation result of theband-stop filter 250. In FIG. 4 , it can be seen that the band-stopfilter reveals a band-stop performance of blocking the local oscillationsignal by about 14 dB or greater at the local oscillation frequency of23 GHz.

FIG. 5 is an exemplary layout of the semiconductor MIMIC forimplementing the FET resistive frequency mixer according to an exemplaryembodiment of the present disclosure. The layout of the MMIC forimplementing the FET resistive frequency mixer may include the FET 210including the source, the gate, and the drain, the LO matching circuit220, the gate biasing circuit 230, the series resonance circuit 240, theband-stop filter 250, the drain grounding circuit 260, the RF matchingcircuit 270, and the IF matching circuit 280. In particular, the seriesresonance circuit 240 and the band-stop filter 250 for enhancing the LOisolation may be disposed between the FET 210 and the matching circuits270 and 280.

FIG. 6 is a graph showing a simulation result for an isolationperformance of the FET resistive frequency mixer including the seriesresonance circuit 240 but not including the band-stop filter 250. TheFET resistive frequency mixer including only the series resonancecircuit 240 revealed an RF-LO isolation of 12.5 dB and an IF-LOisolation of 25 dB. It is understood that the RF-LO isolation is lowerthan the IF-LO isolation by 12 dB or higher because the frequencydifference between the RF signal and the LO signal is greater than thefrequency difference between the IF signal and the LO signal.

FIG. 7 is a graph showing a simulation result for the isolationperformance of the FET resistive frequency mixer including both theseries resonance circuit 240 and the band-stop filter 250. The FETresistive frequency mixer including both the series resonance circuit240 and the band-stop filter 250 revealed the RF-LO isolation of 30 dBand the IF-LO isolation of 35 dB. It can be seen that the RF-LOisolation and the IF-LO isolation revealed improved performances by 17.5dB and 10 dB than the mixer including only the series resonance circuit240.

The device and method according to exemplary embodiments of the presentdisclosure can be implemented by computer-readable program codes orinstructions stored on a computer-readable intangible recording medium.The computer-readable recording medium includes all types of recordingdevice storing data which can be read by a computer system. Thecomputer-readable recording medium may be distributed over computersystems connected through a network so that the computer-readableprogram or codes may be stored and executed in a distributed manner.

The computer-readable recording medium may include a hardware devicespecially configured to store and execute program instructions, such asa ROM, RAM, and flash memory. The program instructions may include notonly machine language codes generated by a compiler, but also high-levellanguage codes executable by a computer using an interpreter or thelike.

Some aspects of the present disclosure described above in the context ofthe apparatus may indicate corresponding descriptions of the methodaccording to the present disclosure, and the blocks or devices maycorrespond to operations of the method or features of the operations.Similarly, some aspects described in the context of the method may beexpressed by features of blocks, items, or devices correspondingthereto. Some or all of the operations of the method may be performed byuse of a hardware device such as a microprocessor, a programmablecomputer, or electronic circuits, for example. In some exemplaryembodiments, one or more of the most important operations of the methodmay be performed by such a device.

In some exemplary embodiments, a programmable logic device such as afield-programmable gate array may be used to perform some or all of thefunctions of the methods described herein. The field-programmable gatearray may be operated along with a microprocessor to perform one of themethods described herein. In general, the methods may be performedpreferably by a certain hardware device.

While the present disclosure has been described above with respect toexemplary embodiments thereof, it will be apparent to those skilled inthe art that various changes and modifications may be made withoutdeparting from the spirit and scope of the present disclosure defined inthe following claims.

What is claimed is:
 1. A frequency mixing device comprising: a fieldeffect transistor (FET) having a gate, a drain, and a source; a localoscillation matching circuit connected to the gate of the FET totransfer a local oscillation signal to the gate of the FET; a gatebiasing circuit connected to the gate of the FET to bias the gate of theFET; a radio frequency (RE) matching circuit having a first terminalconnected to a drain side of the FET and a second terminal serving as aRE terminal to receive or output a RF signal; an intermediate frequency(IF) matching circuit having a first terminal connected to the drainside of the FET and a second terminal serving as an IF terminal toreceive or output an IF signal; a series resonance circuit providing apath from the drain of the FET to ground for the local oscillationsignal to allow a portion of the local oscillation signal passing theFET to flow to ground; and a band-stop filter having a first terminalconnected to the drain of the FET and a second terminal connected to theRF matching circuit or the IF matching circuit to reduce the localoscillation signal transferred to the second terminal of the band-stopfilter.
 2. The frequency mixing device of claim 1, wherein the seriesresonance circuit comprises a capacitor and an inductor connected inseries to each other.
 3. The frequency mixing device of claim 1, whereinthe band-stop filter blocks or reflects at least some portion of thelocal oscillation signal received by the band-stop filter.
 4. Thefrequency mixing device of claim 1, wherein the band-stop filter isdisposed between the drain of the FET and the first terminal of the RFmatching circuit or between the drain of the FET and the first terminalof the IF matching circuit.
 5. The frequency mixing device of claim 1,wherein the band-stop filter is formed in a spiral shape using aspurline.
 6. The frequency mixing device of claim 1, wherein the RFmatching circuit comprises a high-pass filter or a band-pass filterconfigured to deliver a RF output signal having a frequency in which afrequency of the IF signal and a frequency of the local oscillationsignal are mixed.
 7. The frequency mixing device of claim 1, wherein theIF matching circuit comprises a low-pass filter or a band-pass filterconfigured to deliver an IF output signal having a frequency in which afrequency of the RF signal and a frequency of the local oscillationsignal are mixed.
 8. The frequency mixing device of claim 1, furthercomprising: a drain grounding circuit connected to the second terminalof the band-stop filter to provide a path from the second terminal ofthe band-stop filter to ground.
 9. The frequency mixing device of claim8, wherein the drain grounding circuit comprises a radio frequency choke(RFC).
 10. The frequency mixing device of claim 1, wherein the RFmatching circuit or the IF matching circuit comprises a grounding pathconfigured to selectively connect the drain side of the FET to ground.